In order to make aircraft passengers comfortable, and in order to transport them between an airport terminal and an aircraft in such a way that they are protected from the weather and other environmental influences, passenger loading bridges are used which can be telescopically extended and the height of which is adjustable. For instance, an apron drive bridge in present day use comprises a plurality of adjustable modules, including a rotunda, a telescopic tunnel, a bubble section, a cab, and elevating columns with wheel carriage. Of course, other types of bridges are known in the art, such as for example nose loaders, radial bridges, pedestal bridges, dual bridges and over the wing bridges. Additionally, multiple doorways along a same side or opposite sides of the aircraft may be serviced at a same time, for example using the over the wing bridge or two separate bridges.
Manual, semi-automated and automated bridge alignment systems are known for adjusting the position of a passenger loading bridge relative to a doorway of an aircraft, for instance to compensate for different sized aircraft and to compensate for imprecise parking of the aircraft at an airport terminal, etc.
Often, manual bridge alignment systems are preferred by the airlines because a trained bridge-operator is present and is able to observe directly the movements of the bridge relative to the doorway of the aircraft. Typically, the bridge-operator uses a control panel located within the cab section to adjust the bridge each time a flight arrives. Accordingly, the probability that the bridge will collide with an aircraft during an alignment operation is relatively small.
Of secondary concern to the airlines is ensuring that the passenger loading bridge is aligned with the doorway of the aircraft as rapidly as possible, thereby minimizing the time that is required to complete passenger deplaning, cleaning, restocking etc. As such, semi-automated bridge alignment systems are known in the prior art, which systems allow the bridge to be moved rapidly to a preset position under the control of a programmable controller or embedded control system. For example, some passenger loading bridges are equipped with controls that automatically cause the height adjustment mechanism to move the cab to a predetermined height. Unfortunately, the bridge-operator must be present to press a switch for enabling the automated height adjustment. As such, the bridge-operator must arrive at the passenger loading bridge in advance of the aircraft, which wastes the time of the bridge-operator, or alternatively the bridge-operator initiates the height adjustment after the aircraft has arrived at the passenger loading bridge, which inconveniences the passengers that are waiting on board the aircraft.
Schoenberger et al. in U.S. Pat. No. 5,226,204 discloses a semi-automated passenger loading bridge that uses video cameras in the control of the passenger loading bridge. The system maneuvers a movable end of the bridge to a position close to the doorway of the aircraft, whereupon an operator controls the bridge during the last part of its movement by looking at images recorded by the video cameras. Suggestions are made in the patent specification that the system could be arranged to operate in a fully automated manner using image-processing of the recorded images to calculate the distance between the passenger loading bridge and the aircraft. However, image-processing is time-consuming, thus making the movement based thereon slow.
WO 96/08411, filed Sep. 14, 1995 in the name of Anderberg, discloses another device for controlling the movement of a passenger loading bridge. When an aircraft has landed, a central computer, such as for instance a central computer located within a terminal building, transmits information on the type or model of aircraft to a local computer of the passenger loading bridge at an assigned gate. The local computer accesses a local database and retrieves information on the positions of the doors for the type of aircraft that has landed, as well as information on the expected stop position for the type of aircraft at the assigned gate. The retrieved information allows the local computer to determine an absolute position of the door with which the passenger loading bridge is to be aligned. The system also includes sensors for providing real-time positional data for a cab end of the bridge to the local computer. Accordingly, the passenger loading bridge is moved under computer control to a position close to the determined position of the door, for example within 2-10 meters. Optionally, the bridge is preset to this position before the aircraft has stopped moving.
WO 01/34467, filed Nov. 8, 2000 also in the name of Anderberg, teaches that the above system is reliable only for movement to a position close to the aircraft. Thus, the bridge has to be operated manually during the remaining 2-10 meters of its movement. The WO 01/34467 reference also teaches an improvement to the above system, in which electromagnetic sensors are disposed along the distal end of the passenger loading bridge for transmitting a set of electromagnetic pulses in different directions and for detecting electromagnetic pulses after reflection from an aircraft. Based upon the elapsed time between transmitting and detecting the electromagnetic pulses in different directions, a profile of distance as a function of direction is obtained. From the measured distance versus direction profile and the information stored in the computer, it is then possible to maneuver the bridge to the doorway of the aircraft. Unfortunately, the local computer must be in communication with a flight information database of the airport terminal building in order to receive information relating to the type or model of aircraft that is approaching the gate. Such a database must be set up to be accessible by the local computer, and there may be serious security-related issues involved with providing widely distributed access to sensitive flight information. Furthermore, many airports around the world do not support databases that would be suitable for interfacing with a passenger loading bridge system as described by Anderberg. In those cases, the authorities considering an automated passenger bridge would demand a system capable of completely autonomous operation.
Additionally, there are prior art systems for guiding the aircraft to the correct location for docking with a passenger boarding bridge. Fabriksmonteringin Trelleborg AB describe a current state of the art system (http://www.fmt.se). The aircraft parking and information system APIS++ is a laser-based visual docking guidance system used to visually guide a pilot to intercept and establish an aircraft on a gate centerline, and to proceed to a stopping position at an aircraft gate. Real-time azimuth guidance is provided to the pilot by means of a unique Moiré technology azimuth guidance unit. Aircraft type and series information is displayed on an alphanumeric display panel, confirming to the pilot to proceed with the docking maneuver. Aircraft closing rate and stopping position information is provided by a closing rate indicator, which starts a distance-to-go countdown when the aircraft is within close range from its correct stopping position. When interfaced to flight information display systems (FIDS), airports operations database control (AODC) or to air traffic control center (ATCC), APIS++ receives notification that an aircraft has landed. Further provided to the APIS++ is an automatic selection of aircraft type. Advantageously, APIS++ communicates and cooperates with passenger boarding bridges during the process of docking the aircraft. A similar system is described in detail in U.S. Pat. No. 6,324,489, by Millgard, filed Oct. 29, 1999. This system, like the APIS++, provides visual cues to the pilot of an aircraft to assist the pilot in correctly positioning the aircraft relative to the terminal building. The system according to Millgard also makes use of a laser mounted to a stationary fixture to identify and determine the position of the aircraft.
It is a disadvantage of the prior art manual, semi-automated and automated bridge alignment systems that the alignment operation is performed on the basis of observations that are made from a location that is remote to the aircraft. If such observations are erroneous, then the bridge may be allowed to collide unintentionally with the aircraft. Examples of observations that are prone to error include: visually or electronically determining a type of the aircraft; keying in a type of the aircraft into a flight information database; judging the distance remaining between the bridge and the aircraft, etc. Of course, adverse environmental conditions, such as snow, fog, darkness, etc., will greatly increase the likelihood of an erroneous observation.
It would be advantageous to provide a system that simplifies the approach of the aircraft and the docking of the passenger boarding bridge beyond the advances described with reference to the prior art. Further, it would be beneficial to provide members of the flight crew aboard the aircraft some control over the passenger boarding bridge.